A track refers here to a structure that provides a base and direction for an object to move along. More specifically the track refers here to a structure defined by at least two rails that extend and run parallel to each other in a defined direction. An object moving on the track typically comprises some kind of engagement mechanism, for example flanged wheels that allow progress of the object on the rails and retain the moving object on the rails.
In order to achieve smooth progress of the object along the track, the dimensions of the track and the dimensions of the object need to match. When systems applying track delivery are implemented, optimal compliance between the track and the object moving on the track is carefully established. However, during installation or operation of such systems mismatch between these track delivery elements may appear. Such situations are very undesirable and rectifying them easily leads to significant costs.
Dimensioning of track delivery elements is relatively easy when the elements are small and no big forces act upon them. However, also large scale systems that bear and move significant loads apply tracks defined by rails, and with them already initial dimensioning of the track delivery elements is challenging. For example in crane bridges, lateral dimension of the bridge is of the order or meters or tens of meters in comparison with the order of centimeter lateral dimensions of the rail. In addition, the loads carried by the bridge are very heavy so dimensions of the bridge may vary according to whether loaded or unloaded states are in question. It also needs to be considered that the bridge may swing considerably during operation. Variations in the dimensions of the bridge itself may be relatively accurately estimated and anticipated but variations in dimensions of the track are very difficult to control and manage. Furthermore, crane bridges are elevated structures so that the rails typically run in heights. Any installation and service operations in such heights are already inherently challenging. In most cases the rails are also assembled by a different party than the crane bridge manufacturer such that true compliance of the track delivery elements may only be tested when both of these track delivery elements are completely installed.
On the other hand, even if excellent compliance is reached at installation, the situation may change in use. The rails are typically fixed on a foundation, for example a concrete or steel structure or the like. If this foundation for some reason (earth moves, earthquake, material problems) moves, the rails move and dimensions of the track change. Also the track itself may deteriorate or fail during operation. For example, a bolt from rail joints may become loose, and cause a deformation to the rail and thereby to the whole track.
All these reasons may lead to loss of compliance between the track and the bridge, and the severe effects they cause. Primarily, when incompliant track delivery elements are in use, the engaging elements rub against each other and cause wear and tear to the parts. Changing parts of heavy duty elements, for example, crane bridges is very costly and cause disturbances to the production process in which track delivery is applied. In addition, in some advanced track delivery implementations progress of the object is controlled by measurements and drive logics that are based on expected lateral compliance between dimensions of the track delivery elements. When this compliance begins to deteriorate, the drive logic may begin to fail or at least not operate optimally.
In order to avoid these disadvantages, a lot of effort is vested to monitoring dimensional compliance between the track and the apparatus moving along the track. Especially with heavy duty crane systems, the savings both in terms of production down time and maintenance costs is significant if temporal compliance of the track delivery elements can be carefully followed. In practise, monitoring of these type of systems is, however, very difficult. Traditionally, compliance monitoring has basically equalled to track monitoring, i.e. monitoring of the condition and dimensions of the track. Track monitoring is often performed visually, either by a maintenance person practically walking in the elevated track and observing the state of the track, and possibly recording it with a camera. Such visual observations are not accurate and the track and/or facility using apparatus needs to be shut down for the time of the observation. The method is also laborious and risky, so intervals between such monitoring events tend to be too long for practical situations.
In some enhanced solutions, a separate unit is moved along the track to measure its dimensions. In some solutions a separate unit may be fixed to the bridge and moved in front of the bridge to collect measurement information along its way. In other systems, the separate unit is a mobile unit that may be remotely controlled to move along the track and record measured information during its movement. These track measurement systems provide more accurate information than visual observations, but require separately moved measurement entities and require a break to normal operations of the crane bridge. In addition, they only provide information on compliance between track delivery elements when there is no load. The compliance may, in some cases, change quite significantly when load and movements of the bridge resulting from the variably driven load step in. Mere track measurements are no longer sufficient; a more holistic view to the interoperability of the track delivery elements is needed.